Vertical structure of oceanographic parameters in the Eastern Andaman Sea: A model study

The vertical circulation and subsurface variability of the eastern Andaman Sea remain less well-documented compared to surface studies, particularly regarding the relative roles of monsoonal forcing and remotely forced equatorial waves. This study investigated the dominant vertical variability of temperature, salinity, and zonal–meridional currents in the eastern Andaman Sea using validated daily CROCO model outputs from 2015 to 2019. EOF and PSD analyses were applied along the east–west (7.014°N) and north–south (96.45°E) transects to identify the leading modes of variability and their characteristic timescales. Model validation against the observed sea surface temperature and sea surface height demonstrated strong agreement (correlation > 0.9), supporting the reliability of the simulated subsurface fields. The EOF modes reveal that temperature and salinity variability are primarily controlled by seasonal and semiannual monsoon cycles, whereas current variability exhibits strong semiannual and intraseasonal signals. Spectral analyses indicated significant intraseasonal peaks (~30–90 days), consistent with the influence of remotely forced equatorial Kelvin and Rossby waves propagating into the Andaman Sea. Overall, these results highlight the combined influence of monsoon-driven circulation, regional connectivity, and remote equatorial forcing in regulating the vertical structure and temporal variability of the eastern Andaman Sea.